1. Field of the Invention
The present invention generally relates to shotshells and, more particularly, is concerned with a shot charge and wad structure for a military shotgun.
2. Description of the Prior Art
It is convention practice to provide plastic wad structures for use in shotshells to house the shot charge, obturate combustion gases, and cushion the shot charge when the loaded wad is fired from a shotgun and to place a metal disc in the base of such structures to prevent the non spherical projectiles from embedding in or perforating the wad upon setback. One wad structure representative of this practice is illustrated and described in U.S. Pat. No. 3,599,568 to R. J. Shellnut et al. which Patent issued Aug. 17, 1971 and is assigned to the assignee of the present invention. However, when spherical shot is used, such metal discs have not been heretofore used, but rather plastic wads such as in U.S. Pat. No. 3,208,382, Foote et al, issued Sept. 3, 1963. When a shotshell containing one of these structures is loaded in a shotgun and fired, a propellant disposed in the shell tube rearwardly of an obturating Portion of the wad structure is consumed and produces high pressure combustion gases. The pressurized gases act upon the obturating portion, causing it to expand outwardly into sealing relationship with the inner surface of the shell tube and wall of the gun barrel bore. Such sealing prevents gas blow-by and thus increases the chamber pressure generated by a given propellant charge. Since the column of shot pellets contained in a forward shot pocket portion of the wad structure initially resists accelerative forward movement, the "set back" forces are applied by the shot in a rearward direction to the central portion of the base of the wad structure. Then, as the wad structure and shot column are propelled out of the shell tube and start to accelerate through the gun barrel, the shot column pushes radially outward toward the wall of the barrel bore and against the sidewall of the shot pocket portion of the wad structure.
In military shotshell applications, it would be desirable to penetrate metal structures at extended ranges. However, conventional shot wad structures are incapable of withstanding the high level of compressive forces generated by the larger propellant charges and harder pellets needed to penetrate thicker structures. Typically, the pellets become embedded into the plastic base of the shot wad structure when the shotshell is launched upon firing the shotgun.
As a result, the use of flechettes (see the Shellnut et al. patent mentioned above) has been attempted with mixed results. The accuracy of flechettes has not yet been developed to the point of achieving satisfactory results. As a result, the prior combat shotshells all fail to achieve the desired objectives.
Consequently, a need exists to come up with a solution which will overcome the problems encountered with use of prior military shot loads launched at metal penetrating high pressures and velocities.